Large hydrophobic interactions with clearly defined geometry. A dimeric steroid with catalytic properties.

Article abstract of DOI:10.1139/v82-111

The steroid dimer α,α'-bis(17β-(4'-imidazolyl)-11-keto-5α-androstan-3β-amino)-p-xylene, 3, has been synthesized by reductive amination of 17β-(4'-imidazolyl)-5α-androstane-3,11-dione by p-xylenediamine in the presence of sodium cyanoborohydride, and by reductive amination of terephthalaldehyde by 3β-amino-17β-(4'-imidazolyl)-5α-androstan-11-one.The second method is stereochemically unambiguous; the first is not.Compound 3 acts as a catalyst for the hydrolysis of 3-arylpropionate esters of 3-hydroxy-4-nitrobenzoic acid.For the phenanthryl propionate the rateenhancement relative to imidazole is 200-fold, and the rate enhancement relative to the hypothetical rate for the propionate reacting with the steroid by the same transition state geometry is 3000-fold.The slope of a plot k_korr vs. ? for the reaction of 3b with aryl propionate ester was 0.83; the corresponding slope for 12 was 0.39.This provides a design parameter for the construction of artificial enzymes.